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R32 GTR Boost Readings - Apexi PowerFC


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Hello, 

Lately, I have been having a weird issue where when I reach the boost threshold (6000rpm), my car won’t rev past it. It displays my exhaust temp light, I hear somewhat of a scraping sounds and black smoke comes out that exhaust. But only when the light comes on. I checked my boost settings on my PFC and I have my boost set pretty low. Below 1 bar. But on my map, it displays +1.87kg/cm2. That’s not at all what I have my boost pressure set to. My knock readings are below 30 when that happens, my injector duty is in the realm of 70-80. I’m stumped. Could it be the boost controller? I’ll post some pics to show what I mean. 
 

My setup:

GT2860r-5s

Apexi Power FC

Apexi Boost Controller

Nismo 600cc Injectors

That’s it. Everything else is stock. 

 

449A9957-E13C-4FFF-9C37-EAEEC4BA5380.jpeg

72BDCA0B-9655-4571-B0FD-52E17D52E6BF.jpeg

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Your check engine light is your exhaust temp light. You are hitting your fuel cut from over boosting. Quite severely by the sounds of it, as the Power FC fuel cut for boost is preset at 0.25bar above whatever boost you have it set to.

Sounds like no boost to actuators.  Have you got a separate boost gauge to verify ?

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Hang on, in the second photo are you on peak hold after driving or just idling and it's indicating that ? It looks like you are not in peak hold display and just idling, so if that's the case your getting and incorrect MAP sensor reading to the ECU.

The Apexi MAP sensor is a 0 - 5v 3bar Denso unit, so it supports 2 bar positive boost. Sounds like the MAP sensor could be stuffed or a wiring problem. Somehow the signal wire at your ECU end could have 5v on it from a wiring short or again an internally stuffed MAP sensor, as your reading is very close to having a maxed MAP sensor signal.

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28 minutes ago, BK said:

Hang on, in the second photo are you on peak hold after driving or just idling and it's indicating that ? It looks like you are not in peak hold display and just idling, so if that's the case your getting and incorrect MAP sensor reading to the ECU.

The Apexi MAP sensor is a 0 - 5v 3bar Denso unit, so it supports 2 bar positive boost. Sounds like the MAP sensor could be stuffed or a wiring problem. Somehow the signal wire at your ECU end could have 5v on it from a wiring short or again an internally stuffed MAP sensor, as your reading is very close to having a maxed MAP sensor signal.

The second picture is the car at idle. So, what would be faulty? Would a false reading affect actual boost output? 
I have limited knowledge on this. 

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1 hour ago, BK said:

Have you got a separate boost gauge to verify ?

I doubt your solenoid is doing anything to control boost as your settings look whack. You can't have 0.8 bar and have 50 odd duty cycle as it won't do anything, but this isn't the problem or related in any way.You need a different gauge for a start to know what the real vac/boost is as your hand controller boost reading is not correct (you're not boosting at 1.8+ bar at idle are you ?)

I also said what is probably going on and faulty -

56 minutes ago, BourneToLive said:

The Apexi MAP sensor is a 0 - 5v 3bar Denso unit, so it supports 2 bar positive boost. Sounds like the MAP sensor could be stuffed or a wiring problem. Somehow the signal wire at your ECU end could have 5v on it from a wiring short or again an internally stuffed MAP sensor, as your reading is very close to having a maxed MAP sensor signal

If you don't understand the above you'll need to take it to someone that does, but I'll try one last time to elaborate.

The Apexi boost control kit that integrates to the Power FC is literally just a 3 port solenoid to control boost pressure to your actuators and a 3bar MAP sensor to actually read the boost and give that signal to the ECU and display on your hand controller. The boost solenoid just plugs into the original 2 wires for boost control. The 3 bar MAP sensor is 3 wires (5v power, a negative and a signal) and is run back in new wiring to a new 3 pin plug on the ECU.

The 3 bar MAP sensor is scaled for its output to the ECU as 0 - 5v linear signal.  This means at 4.5 - 5v on the signal wire at the ECU end will indicate 1.8 - 2.0 bar of boost. The only way your hand controller could indicate this is if the signal wire has indeed above 4.5v on it at idle (which it shouldn't). 3 things would cause this:

1. MAP sensor wiring problem physically shorting the 5v to the signal wire

2. MAP sensor internally failing and shorting the 5v to it's signal output

3. ECU internal problem shorting 5v to the boost signal pin.

All electrical problems. I have had a Denso / Apexi 3bar MAP sensor fail in the past, but exactly the opposite problem - MAP sensor would not output anything on its signal wire.

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On 5/6/2021 at 10:24 AM, BK said:

I doubt your solenoid is doing anything to control boost as your settings look whack. You can't have 0.8 bar and have 50 odd duty cycle as it won't do anything, but this isn't the problem or related in any way.You need a different gauge for a start to know what the real vac/boost is as your hand controller boost reading is not correct (you're not boosting at 1.8+ bar at idle are you ?)

I also said what is probably going on and faulty -

If you don't understand the above you'll need to take it to someone that does, but I'll try one last time to elaborate.

The Apexi boost control kit that integrates to the Power FC is literally just a 3 port solenoid to control boost pressure to your actuators and a 3bar MAP sensor to actually read the boost and give that signal to the ECU and display on your hand controller. The boost solenoid just plugs into the original 2 wires for boost control. The 3 bar MAP sensor is 3 wires (5v power, a negative and a signal) and is run back in new wiring to a new 3 pin plug on the ECU.

The 3 bar MAP sensor is scaled for its output to the ECU as 0 - 5v linear signal.  This means at 4.5 - 5v on the signal wire at the ECU end will indicate 1.8 - 2.0 bar of boost. The only way your hand controller could indicate this is if the signal wire has indeed above 4.5v on it at idle (which it shouldn't). 3 things would cause this:

1. MAP sensor wiring problem physically shorting the 5v to the signal wire

2. MAP sensor internally failing and shorting the 5v to it's signal output

3. ECU internal problem shorting 5v to the boost signal pin.

All electrical problems. I have had a Denso / Apexi 3bar MAP sensor fail in the past, but exactly the opposite problem - MAP sensor would not output anything on its signal wire.

It turned out to be the first one. Took it to a specialist in my area and it was a short in the wire from the sensor to the ECU. A body shop I took my car to probably nicked the cable. A new cable fixed the false reading of 1.87kg/cm2. I wonder if the problem of not being able to boost past 6000rpm is still there. 

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4 hours ago, BourneToLive said:

It turned out to be the first one. Took it to a specialist in my area and it was a short in the wire from the sensor to the ECU. A body shop I took my car to probably nicked the cable. A new cable fixed the false reading of 1.87kg/cm2. I wonder if the problem of not being able to boost past 6000rpm is still there. 

Good one, glad you got it sorted. Anyway remember what I said about boost cut being 0.25bar above your setting ? I bet the boost setting you are in is too low, triggering the boost cut. Raise it to 1.0 - 1.1 and see how you go.

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5 hours ago, BK said:

Good one, glad you got it sorted. Anyway remember what I said about boost cut being 0.25bar above your setting ? I bet the boost setting you are in is too low, triggering the boost cut. Raise it to 1.0 - 1.1 and see how you go.

You’re right! I didn’t know that about the Apexi, until now. It came installed in my car and I never messed with it. I just took it to a tuner. That explains it. I set it to 1.1 bar and it still feels like it lacks in power, but it didn’t cut like before. The -5s are more high-end power, and I couldn’t safely hit 6000rpm. Anyway, these are the results. Thanks for the help, brother. 

9C6169B3-E3C7-4D3F-A6D1-1001C236EB1F.jpeg

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